The Graph API as such allows you to easily access all public information about an object. For example, https://graph.facebook.com/btaylor (Bret Taylor) returns all the public information about Bret. For example a user's first name, last name and profile picture are publicly available.

To get additional information about a user, you must first get their permission. At a high level, you need to get an access token for the Facebook user. After you obtain the access token for the user, you can perform authorized requests on behalf of that user by including the access token in your Graph API requests